1. Technical Field
The present invention relates to a cylindrical columnar or tubular magnetized bonded magnet structure with N and S poles being alternately provided in the axial direction.
2. Background Art
In various fields, columnar or tubular magnets are used which have a plurality of permanent magnet members that are arranged with their same polarity sides being opposed to each other. For example, they are used in a foreign matter removal device for removing iron powder and the like from food, and a stator for linear motors (see Japanese Patent Laid-Open Publication Nos. JP 2003-303,714 A; JP 2005-73,466 A; and 3,952,190 B). In such columnar or tubular magnets, the N and S poles are alternately arranged on the outer peripheral surface in the axial direction so that magnetic lines of force radially extend from each magnetic pole. In such magnets, magnetic poles appear on the outer peripheral surface. For example, as for an N pole, magnetic lines of force radially extend from the N pole in the direction perpendicular to the axial direction, and then curve toward an S pole adjacent to the N pole along long arc lines. Accordingly, many magnetic fields can be produced along the outer peripheral surface of the columnar or tubular magnets. For this reason, when such magnets are used for linear motors or linear actuators, it is possible to provide strong propulsion force. Hereinafter, such magnets are referred to as alternately-magnetized multipolar magnets.
In the case where a stator is constructed of a columnar or tubular cylindrical alternately-magnetized multipolar magnet and used for a linear motor or linear actuator, a slider of the linear motors or linear actuator has a coil that is arranged concentrically with and perpendicularly to the axial direction of the columnar or tubular alternately-magnetized multipolar magnet (see JP 2005-73,466 A; and 3,952,190 B). The slider can be propelled in the axial direction of the columnar or tubular alternately-magnetized multipolar magnet by interaction between a current that flows in the coil and magnetic fields that are produced by the permanent magnet of the stator.